The present invention concerns a method of continuously preparing masses, especially masses of chocolate, that contain cocoa butter or other fats, for processing, in a tempering machine with a cooling section that has several cooling stages and a reheating section that has several reheating stages, which the mass travels through while being cooled in the cooling section and reheated in the reheating section. The device for carrying out the method involves a tempering machine with a series of several cooling stages, each of which has compartments for processing the mass and contain mixers and stirrers and which together constitute the cooling section, wherein the mass is cooled by heat exchange with heat-exchange surfaces in conjunction with a coolant that is connected to a circulation system, subsequent to which the mass is advanced to a reheating section that consists of a series of several reheating stages, each of which has compartments for processing the mass and contain mixers and stirrers and which together constitute the reheating section, wherein the mass is reheated by heat exchange with heat-exchange surfaces in conjunction with a tempering fluid that is connected to a circulation system.
A method and a device of this type are known from European Exposure 289 849. The amount of coolant flowing through the cooling stages is kept high enough to generate turbulent flow. The mass is blended thoroughly enough in the compartments by mixers and stirrers contained in them to generate turbulence accompanied by a relatively high shear rate in the interval between the heat-exchange surfaces and the stirrers. The amount of coolant recirculated through the cooling compartment is constant. The coolant is continuously recirculated. The temperature of the coolant is maintained within a comparatively narrow range. The temperatures employed at the coolant end are relatively high in absolute terms due to the improved heat transfer. They range from 16.degree. to 22.degree. C. The mass is accordingly cooled to an ultimate approximately 28.degree. to 29.degree. at the end of the cooling section and beginning of the reheating section. The result is the highest possible number of stable crystals in the .beta. form. In the next reheating section, a tempering medium travels through a tempering circulation system, wherein its quantity and temperature are maintained constant and a temperature within the range of 31.5.degree. to 33.degree. C. is employed for a very wide range of applications. The mass leaves the reheating section at a temperature of approximately 31.5.degree. to 32.5.degree.. Since this mass-exit temperature is approximately 2.degree. higher than previously known, the properties needed for further processing are improved. The ratio of the area of the heat-exchange surfaces in the cooling section to those in the reheating section can be approximately on the order of 1:1, meaning that the cooling section and reheating section can be more or less the same size. The number of cooling stages in the cooling stage and or reheating stages in the reheating section depends on the desired rating that the tempering machine is designed for. When a tempering machine of this type is operated, say, at its rated output or even at approximately 80 to 110% of its rated output, the properties will be outstanding and the mass will be well tempered accompanied by such overall advantages as good contraction, luster, crispness, etc., associated with a comparatively high percentage of stable crystals in the .beta. form. When on the other hand such a tempering machine is operated for example at only 40 to 75% of its rated output, the tempering will be less satisfactory. This can be ascribed to the necessity for the temperature of the coolant in the cooling section to be more than approximately 22.degree. to prevent the smaller throughput of mass from being excessively cooled at the end of the cooling section. This is valid for methods wherein the coolant is continuously recirculated in the cooling section. In tempering machines wherein the coolant is discontinuously recirculated as the system is turned on and off, the "out" times will lengthen in relation to when the coolant is flowing through the cooling section. The result is discontinuities in temperature and in temperature degrees that lead to different degrees of germination because the temperature of the coolant also climbs to over 22.degree. during out times. The mass can also not be well tempered to this extent.
Also known are tempering machines wherein the cooling section is more extensive and even substantially more extensive than the reheating section, with the heat-exchange surfaces in the cooling section having approximately twice as much area as those in the reheating section. It is known in conjunction with such tempering machines to divide the cooling section and shut down some of the divisions where the mass enters the cooling section when the machine is operated at low output. This is accomplished by adding the first cooling stage of the cooling section to the circulating heating system that protects the intake into the tempering machine. It is accordingly only the subsequent stages in the cooling section that do the cooling, and the heat-exchange surface in the cooling section is less extensive, so that the coolant can otherwise be controlled as usual. The result is that the germination will be just as satisfactory at reduced output as it is at full-scale operation.
German Patent 2 536 063 discloses a continuous-operation tempering machine with a number of separate cooling stages followed by a homogenization compartment with a different shape that can be heated by a tempering circulation system such that the mass can be powerfully blended without increasing its temperature very much. Differences in the temperature of the mass are eliminated and the crystals are uniformly distributed throughout the mass. The low melting-point crystals also have time and opportunity to melt and change to higher melting-point crystal types.